Hydraulic classification of solids



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Sept. 27, 1949. N. L. DAvls ET AL HYDRAULIC CLASSIFICATION OF SOLIDS 7 Sheets-Sheet 2 Filed May 26, 1.945

W W m Sept. 27, 1949. N. DAvls yET AL HYDRAULIC CLASSIFICATION OF SOLIDS 7 Sheets-Sheet 3 Filed May 26, 1945 Summa Sept. 27, 1949. N. L.. DAvls ET AL HYDRAULIC CLASSIFICATION OF SOLIDS '7 Sheets-Sheet 4 Filed May 26, 1945 00000 000000 0 000000000000 00000 00000 00 00000 00 00000 00000 000 00 00 00000 oo 00000 00000 0000000 0000 00.000 oo 00000 0 000000 000000000000 000000 000000 000 c0000 0 0000000 000 0000000000 0000000000 0000000000 000000 0000 0000000 000 0000000 000 o 0000 00 000 000 00 00000 0000 oo 0 000 000000 000 ttomw@ Sept. 27, 1949. N. L. DAvls ET Al. 2,482,747

HYDRAULIC CLASSIFICATION 0F soLIDs Filed May 26, 1945 '7 Sheets-Sheet 5 Sept; 27, 1949. N. I .pAvls ET Al. 2,482,747

HYDRAULIC CLASSIFICATION OF SOLIDS Filed May 26, v1945 7 sheets-sheet e C/HCULAT//VG PUMP gmc/who@ Sept. 27, 1949. N. DAvls ET Al.

HYDRAULIC CLASSIFICATION F SOLIDS '7 sheets-sheet 7 Filed May 26, 1945 Patented Sept. 27, 1949' Nelson L. Davis and Hilmer N. Ekbom,

and Laurance 0. Millard,

Chicago, La Grange, lll., as-

signors to Link-Belt Company, a corporation of Illinois Application May 25, 1945, Serial No. 595,934

28 Claims.

'Ihis invention relates to methods and apparatus for hydraulically classifying solids, and deals more specically with the separation of such materials as raw coal, ore, or the like, into different classifications or products of dierent specific gravities.

The present day demands for a greatly increased production of coal with a reduced supply of labor in the mines have resulted in abandoning the prior methods employed for mining coal.

Because the method and apparatus embodying this invention are particularly well adaptedfor effecting three product separation, or classification, of present day run-of-the-mine coal, they will be described primarily with this use in mind. However, as the detail description proceeds, it will be apparent to those skilled in the art that the apparatus disclosed is adapted-for carrying out methods for separating, or classifying, other materials than coal, and that methods for effecting two product separation, or classification, of

suitable materials, also, may be performed.

The raw bituminous coal now being mechanically mined is an ideal material to be classified into three products by hydraulic methods and apparatus employing parting, or heavy, density liquids because the coal that is free of commercially objectionable impurities can be labora.- tory tested for the determination of the proper specific gravity for a liquid on which it will float. Specific gravities thus determined have been found in practice to vary, and itis not uncommon to find this specific gravity to be 1.35 in some cases while in other cases it may be as high as 1.45. Similarly, reject material from mechanically mined coal has been determined as having no commercial value when it will sink in testing liquids which, in some cases, may be 1.55 and in other cases, as high as 1.70. It is therefore apparent that between the specic gravities at which the purer coal and the rejects are separated, there exists a so-called middlings product, which is either a high ash bone coal, purer coal clinging to laminations of slate; or a combination of bone and laminated coal. Once isolated as a third product, this middlings material can be sold as a second quality fuel where it is mainly comprised of bone coal, or, if laminated, it may be crushed for the freeing of the purer coal from its slate laminations and re-treated for the recovery of the fuel values it contains.

It is the primary object of this invention to provide a high capacity method of and apparatus for hydraulically classifying solids on a continuous basis into several different products of difeffecting a three product ferent specific gravities and delivering the products for subsequent handling or use as actually classified and without the loss of an economically prohibitive quantity of the separating liquid.

A further important object of the invention is to provide apparatus for hydraulically classified solids which occupies a minimum amount of space; which may be installed at a low initial cost for the separating equipment; and which does not include any moving equipment parts that are submerged in the parting liquid.

Still another important object of the invention is to provide a method of and apparatus for separation of solids, such as coal, by means of asingle make-upof parting, or heavy density, liquid in a single separating or classifying vessel by first effecting in a quiescent zone in said vessel a clean float and sink classification of the purer coal from the remainder of the starting material and by then effecting a clean classification of the resultant sink material into middlings and refuse by projecting through its path of descent an injected stream of the parting, or heavy density, liquid in the form of a subsurface current of proper strength, proportions, and direction to effect a relatively lateral displacement of the slower sinking middlings from the more rapidly sinking valueless refuse so that these two relatively displaced products will finally sink into their respective zones of removal from the vessel.

A further object of the invention is to manipulate the single make-up parting liquid, such as by its recirculation, the like, as to exercise a definite control over the rate of settling of the comminuted particles, suspended in the liquid to increase its density, so that the liquid in different portions or zones of the separating vessel maybe maintained either at the same specific gravity or at different specific gravities.

Another object of the invention is to control the specific gravity of the parting liquid, as referred to above, in either or both of the zones of removal of the middlings and refuse so that their separation by relatively lateral displacement is supplemented by the sink and fioat action of the liquid.

Still another object of the invention is to direct the above referred to subsurface current through the separating vessel in such a direction that it will discharge with, and assist the discharge of, the float or purer coal from the vessel.

It is quite obvious that one goal to strive for, in designing a hydraulic classification system, is to hold to a minimum the volume of parting, or

replenishment, agitation, or

mean? heavy density, liquid required in relation to the capacity of the separating vessel. This is Important because it determines the cost of the heavy density material that is used to produce the parting liquid; because it determines the time involved in stabilizing the liquid at the desired specic gravity, or density, when the system is started in operation; and because it determines the ability to maintain the stability of the liquid during a prolonged period of operation.

It is a further important object of the invention to provide a separating vessel of such shape and size, and to so effect the stabilization of the parting liquid during operation of the system, that the volume of the liquid relative to the capacity of the vessel is reduced to a minimum.

As the introduction of a stream of the parting liquid into the vessel to produce a subsurface classifying current constitutes the principal way in which withdrawn liquid is returned to the vessel, it is a further important object of the invention to provide a separating vessel of such shape and capacity as to cause the ratio of the volume of the vessel to the volume of the subsurface current, per minute of time, to be either equal to or less than to 1.

Another primary object of the invention is to provide apparatus which may be operated, without structural modification, to carry out either one of three different hydraulic classification methods; i. e., separation of the solids into three products by the combined use of the principles of sinlr` and float and of relatively lateral displacement of products having different sinking velocities; separation of solids into two products by the independent use of the principle of sink and float; and separation of solids into two products by the independent use of the principle of relatively lateral displacement of products having different sinking velocities.

Other objects and advantages of the invention will be apparent during the course of the following description.

In the accompanying drawings, forming a part of this specification, and in which like numerals are employed to designate like parts throughout the same,

Figure 1 is a side elevational view of the apparatus involving this invention which is capable of carrying out the above referred to methods of hydraulically classifying solids into separate products of different specic gravities,

Figure 2 is a top plan view of the apparatus disclosed in Fig. 1,

Figure 3 is a transverse vertical sectional view taken through the separating vessel portion of the apparatus shown in Figs. 1 and 2,

Figure 4 is a vertical sectional view taken on line 4--4 of Fig. 3,

Figure 5 is a horizontal sectional view taken on line 5-5 of Fig. 3,

Figure 6 is a detail, perspective view of the piping, or circulating, system for the parting, or heavy density, liquid employed to effect hydraulic classication of solids in the apparatus disclosed in the previously referred to gures,

Figure 'l is a vertical sectional view taken through the separating vessel and employed to illustrate the displacement action, on lumps of sink material of different sizes and specific gravi- 4 into substantially V-shaped,

ties, produced by the subsurface current of parting liquid,

Figure 8 is a detail perspective view of the discharge portion of a conveyor casing plate which forms a part of the apparatus shown in preceding figures, and

Figures 9 and 10 are detail sectional views of the conveyor wheel which is employed for removing the separated middlings and refuse from the separating vessel.

In the drawings, wherein for the purpose of illustration is shown the preferred embodiment of this invention, and first particularly referring to Figs. 1 to 5 inclusive, there is disclosed a supporting framework which includes the four I-beam corner posts or uprights II which have suitably connected to their upper ends the parallel, horizontally extending, supporting I-beams I2 which extend longitudinally of the installation assembly illustrated more particularly in Figs. 1 and 2. Figs. 1 to 4 inclusive disclose two additional, transversely extending, I-beam frame members I3 which are connected at their opposite ends to the longitudinal beams I2.

Figs. 1 to 5 inclusive may best be referred to for a disclosure of the separating vessel structure. This structure includes what will be termed a feed end plate I4, a discharge end plate I5, a false bottom plate I6, and the combined side and true bottom forming plates I1 and I'8. To describe this vessel structure more in detail, it will be pointed out that the feed and discharge end plates I4 and I5 respectively are of general rectangular shape in elevation and are suitably connected at their vertical edges to the frame uprights II. Their bottom edges are connected to the longitudinal edges of the bottom plate I6 by the angle irons I9. The combined side and true bottom wall plates I1 and I8 are best illustrated in Fig. 3 as including the vertical top portions 20 and 2| respectively, the curved intermediate portions 22 and 23 respectively, and the straight bottom portions 24 and 25 respectively. These straight portions 24 and 25 are illustrated in Fig. 3 as converging downwardly. Figs. 1 and 2 disclose these portions 24 and 25 as being formed spaced portions which form the opposite sides of two ducts 26 and 21. The remaining two sides of these ducts are formed by the additional plates 28, 29, 30 and 3|.

By considering the several views, it will be seen that this separating vessel is open at its top and is of rectangular shape in plan. It is approximately twice as wide as it is long and, as seen in vertical section in Fig. 3, it partially assumes the contour of a circle. When filled to the water level 32, indicated in Fig. 4, the vessel now consideredto be the preferred size will have a volumetric' capacity of approximately 3100 gallons of liquid.

The feed end plate I4 is provided at its upper portion with a flanged feed opening 33 to which is connected the feeder sluice or trough 34 for the starting material, which may be raw or run-ofthe-mine coal. This feed sluice or trough 34 is illustrated in Figs. l and 2 as being connected at its outer end to piping of the liquid recirculating system which will be described in detail at a later point. Consequently, liquid will be delivered to the starting material to wet down the same and assist in its delivery. A flow deilecting plate 35 is positioned in the receiving end of the sluice or trough 34 to direct the liquid downwardly toward the bottom of the trough.

The feed end plate I4, also, is provided with a flanged inlet opening 36 for connection with the liquid recirculating piping or system, that will be described in detail at a later point. This liquid inlet opening 36 is so arranged and directed that its axis, if it were projected through the separating vessel, would pass Just above the weir 31 of the outlet opening 36 which is provided in the discharge end plate I `at its top and directlyopposite the starting material and parting liquid inlet opening 33. A discharge trough 39 is connected to the outlet opening 36 andv functionsto carry away the iloatproduct that is classified in the vseparating chamber and a desired portion of the parting, or heavy density, liquid, for disposal in a manner to be vdescribed at a later point.

Figs. 3, 4 and 5 disclose the transverse frame beams I3 as having secured thereto, to depend therefrom, mounting frames 40 which support the bearings 4I in which are journaled two parallel shafts 42. These shafts have mounted thereon the flanged rollers 43 which function to support-the conveyor wheel which operates for the most part within the separating vessel.

This conveyor wheel-is best illustrated in Figs. 3 to 5 inclusive, 9 and 10. The wheel consists of three spaced, parallel, annular rings or plates which are identified bythe reference characters 44, 45 and 46. 'Ihe rings or plates 44 and 46 constitute the opposite ends of the conveyor wheel while the ring or annular plate 45 constitutes a I middle partition which separates the interior of the wheel into two parts.

These three rings or annular plates 44 to 46 are interconnected and braced by means of the flight plates 41, the mounting strips 48 for the peripheral edges of the ights, and the angle strips 49. The periphery of the conveyor wheel is bridged by the wire mesh 56. It will be seen, therefore, that this conveyor wheel is made up of two circular series of conveying pockets which open inwardly.- The sides of these pockets are formed by the flights 41 and the three rings or annular plates 44, 45 and 46. The perlpheries of these l pockets are closed against the passage of conveyed solids by the wire mesh 56. p

Figs. 3 to 5 inclusive and 9 disclose the inner edges of the rings or annular plates 44 and 46 as having bolted, or otherwise suitably secured thereto, the spacer rings 5I, the sprocket rings 52 and the track rings 53. The track rings .engage the flanged rollers 43. for supporting the conveyor wheel in position with respect to the separating vessel.

By considering Figs. 2 to 5 inclusive, it will be seen that the conveyor wheel is driven in a counterclockwise direction, as viewed in Fig. 3, by means of the two sprocket chains. 54 that are trained over the sprocket wheels 55 carried by shafts 56 which are journaled in bearings 51 mounted on the transverse beam members I3. This driving of the conveyor wheel is accomplished by the lower runs of the chains 54 meshing with the teeth of the sprocket rings 52 that are attached to the opposite ends of the conveyor wheel.

Figs. 2, 3 and 4 best illustrate one of the 4shafts 56 as having mounted thereon a drive sprocket wheel 56 over which is trained a sprocket chain 59 that is driven by the sprocket pinion 60 mounted on the driven shaft 6I of the speed reducer unit 62. This speed reducer unit 62 is best illustrated in Fig. 2 as having its drive shaft 63 coupled to the armature shaft of i the electric motor, orother prime mover, 64. This drive mechanism ismounted on the bracket 65 that is attached to two of the uprights or frame members II.

When the conveyor wheel is rotated, the two annular series oi' conveying pockets are intended to receive classified or separated solids as they pass through the bottom portionof their annuv lar path and these pockets are intended to discharge the conveyed solids as they pass through the ltop portion of their annular path. It is necessary, therefore, to encase or close the openings of these pockets while the pockets pass through the active or conveying side of their path. To accomplish this, a curved plate 66 is provided and is secured at its longitudinal edges to the end plates I4 and I5 by the flanges 61. When the conveyor wheel is functioning to remove two diiferent separated, or classified, products from the separating vessels, the two products are separately conveyed in the two annular series of conveying pockets. To keep these two products separated when they are dischargedfrom the conveyor wheel, the'two annular series of conveying pockets are caused to discharge at two peripherally spaced zones by extension plates which are associated with the upper edge oi' the curved plate 66. These extension plates are best illustrated in Figs. 3 to 5 inclusive and 8.

These ,extension plates vconsist of an inner plate section 66, which bridges the inner sides of both annular series of conveying pockets, and the outer. plate section 69 which bridges the annular series of conveying pockets that are arranged on the discharge end of the conveying wheel. The platesection 66 is provided with a discharge lip 16 which is attached to the transverse supporting bracket 1I. Figs. 5 and 8 discloses a mounting arm 12 which is carried by the righthand end portion of the full width extension plate 68 for supporting this plate on the angle bracket 1I. The inner edge of the full width, extension plate section 66 is supported by a plurality of angular feet 13 which are illustrated in Figs. 3 and 5 as being attached to a trough 14 that extends from side to side through the separating vessel and within the annular path of the conveyor wheel. Fig. 3 discloses this trough 14 as being inclined so as to discharge at the inactive or return side of the conveyor wheel. This trough is intended to receive parting, or heavy density, liquid which the conveyor wheel, acting as a pump, delivers thereto. The

vliquid received by this trough 14 is returned to the inactive side of the conveyor Wheel. The discharge end of the trough meets the upper end of a curved plate 15 which follows the return path of the conveyor wheel. This plate terminates in spaced parallelism with the lower edge of the previously referred to curved plate 66. The adjacent bottom edges of these plates 66 and 15, therefore, form a feed opening through which classied solids are delivered to the pockets of the conveyor Wheel.

Figs. 3 and 4 disclose two downwardly converging grill or grid plates 16 as being arranged within the annular path of the conveyor wheel. These plates function to confine or direct the classified solids to the feed opening for the conveyor wheel.

Figs. 1, 3 and 4 disclose an adjustable divider plate 11 which is hingedly mounted on the shaft 16 that is journaled at its opposite ends in suit- The separated. or classified, solids that are discharged from the two annular series o! conveyor pockets, over the free edges of the plate sections 68 and 69, are conveyed away in their separated condition. To effect this conveyance of the classiied products, Figs. 3 and 4 illustrate a conveyor trough 82 which is divided into two compartments 83 and 84. The compartment 83 is intended to receive the solids that are discharged over the free edge of the sectional plate 88. The compartment 84 receives the classied solids that are discharged over the vfree edge, and lip 10, of the plate section 89. Each one of these conveying compartments 83 and 84 have the nights 85 and 86, respectively, moving therethrough to carry away the solids that are fed into the compartment. These ilights are attached to the cross bars 81 which are c arried by the parallel conveyor chains 88. Figs. 1, 2 and 4 disclose a conveyor foot shaft 89 that carries the two foot sprocket wheels 90 over which the conveyor chains 88 are trained. n

Figs. 1 and 2 disclose the discharge trough 39 as emptying into a suitable vibrating screen box 9|. This screen box is suspended by suitable cables, or the like, `92 that are attached at their upper ends to spring brackets 93 carried by the longitudinal beams |2. A vibrator unit 94 is suitably attached to the screen box 9| and is driven by the belt 95 that is trained over the drive pulley 96 of the electric motor, or other prime mover, 91 that is suitably supported on the longitudinal frame beams |2. This vibrating screen 9| receives the iloat product from the separating vessel and a predetermined amount .of the parting, or high density, liquid. The iloat product Will be discharged from the end of the vibrating screen while the parting, or heavy density, liquid will pass through the screen cloth into the liquid sump 98. It will be explained how the liquid from this sump is recirculated, or fed back to the separating vessel by means of two fluid pumps and a series of circulating pipes. It will be appreciated, therefore, that the liquid level in the separating vessel will be higher than the liquid level in the sump 98. The sump, therefore, should have a capacity that will enable it to receive the liquid which will drain out of the separating vessel when the pumps are stopped and the liquid level in the separating vessel and the sump are the same.

The recirculation of the parting, or heavy density, liquid from the sump 98 to the separating vessel is accomplished by the piping and pumping circuits that are best illustrated in Figs. 1, 2 and 6 and will be described in detail in connection with these gures.

The bottom discharge opening of the sump 98 is connected to the coupling member 99. The opposite ends of this coupling member communicate with the valves |00 and |0| respectively. The valve |00 is connectedby a short pipe section |02 to an elbow |03 that is suitably coupled to the inlet of a pump unit |04. The outlet of this pump unit is connected by the elbow |05 to the pipe line |06. The outer end of this pipe line is connected by an elbow |01 to a pipe section |08 which is connected at its outer end to the T |09. The valve |0| is connected to the elbow ||0 which in turn is connected to the pipe line The outer end of this pipe line is coupled to the inlet of a second pump unit ||2. The outlet of this pump unit is connected by the elbow I3 and the short pipe section I4 to the T |09.

The outlet branch of the T |09 is connected by the Y-coupling I l5 through one of its branches by way of the trough 34 and the inlet 23, pri-l to the valve ||8 and through its other branch t0 the valve ||1. The downstream side of the valve H6 is connected by the flanged, flaring nxture ||8 to the inlet opening 36 of the separating vessel. The valve ||1 is connected by the short pipe section ||9, the coupling |20. and the short pipe section- |2| to the manifold |22 that has its various outlet branches ,|28 opening into the receiving end .of the feed trough or sluice 34.

The pipe line |06 is connected by the branch lines |24 and |25 to the valves `|26 and |21 respectively. The downstream sides of these valves are connected to the Ts |28 and |29, respectively. The pipe line has connected thereto branch lines |30 and |3|. The ends of these branch lines are connected to the elbows |32 and |33 respectively which in turn are connected by pipe sections |34 and |35 to valves |36 and |31 respectively. The remaining openings of these valves |36 and |31 are connected to branches of the Ts |28 and |29 respectively. By inspecting Figs. 1 and 4, it will be seen that the T |28 is connected to the bottom opening of the duct 21, formed in the bottom of the separating vessel, while the T |29 is connected to the bottom opening of the duct 26.

The recirculation of the parting, or heavy density, liquid may be accomplished in the Iollowing way:

A suitable quantity of parting liquid, of the desired specific gravity, is placed in the sump 98 and the separating vessel. If run-of-themine coal is to be separated, or classified, into three products, the specific gravity of the parting liquid should be established as proper for floating the purer coal. The remainder ofthe starting material, which will be separated into refuse and middlings, will sink in this liquid.

To prepare the parting liquid, calcium chloride, or -other chemical salts, in solution may be employed or such commlnuted solids as sand, ferro-silicon, magnetite, or the like, can be suspended in water. Of course, the proper proportions of water and the density increasing medium will be employed to provide the specic gravity liquid that is desired.

The original charge of parting liquid may be delivered to the system in any desired manner. During continued operation of the system, regulated amounts of the liquid in circulation will be withdrawn from any desired portion of the system to permit the liquid to be cleaned and reconditioned. and a, like amount of fresh makeup liquid will be charged into the system, in any desired manner, to maintain a constant total volume of liquid in the system during all operating periods. No attempt has been made to disclose the withdrawal and replenishing pipe lines as they may be connected to any of the illustrated circulation pipe lines, depending upon the layout of each complete coal cleaning installation.

Because a constant volume of the parting liquid will be leaving the separating vessel during the entire operating period of the apparatus, by passing over the weir 31 with the float coal, a like quantity of the liquid should be returned to the separating vessel, from the sump 98, to maintain the liquid level that is illustrated in Fig. 4 and identied by the reference character 32. The subsurface current directing inlet opening 36 and the delivery of the parting liquid to the separating vessel with the starting material,

\ mamy 3100 gallons.

9 marily are relied upon for returning. the/proper amount of liquid to the s epgratigyes'sel.

The parting liquid is delivered-to the subsurface current directing inlet 36/ through the funnel-shaped coupling ||8, the ilow regulating and controlling valve H6, and the Y-coupling ||5. The parting liquid is delivered to the starting material feed trough 3-4 by the manifold |22, the pipe members ||9, |20 and .|2|, the ow controlling and regulating valve ||1, and the Y- couplingl ||5. This last mentioned coupling,

therefore, is common to both of the means employed for delivering the parting liquid to the separating vessel.

The parting liquid is delivered to the Y- coupling ||5 by both of the pumps |04 and ||2. The 'pump |04 receives the parting liquid from the sump 98 through the iiow controlling and regulating valve and the pipe members |02 and |03. This pump delivers the liquid to the Y-coupling through the pipe line |06, the coupling |01, the pipe sectionrlll, and the T |09. The pump ||2 receives liquid from the sump 98 through the flow controlling and regulating valve |0| and the pipe members ||0 and This pump delivers the liquid to the Y-coupling ||5 through the pipe members ||3 and 4. Y

The liquid flow regulating and controlling valves ||6 and ||1 function to control the division of the recirculating liquid between the subsurface current inlet opening 36 and the starting material feed trough 34. The valves |00 and |0| are provided for regulating the hydraulic intake head of the two pumps |04 and ||2 so that they are kept in proper hydraulic balance. If other than centrifugal pumps are used these valves may be omitted.

The diagonally directed, subsurface current that is created in the separating vessel should be regulated, or varied, in accordance with theA lump sizes of the solids that are to be classified in the separating vessel. That is tosay, different rates of flow are required for the subsurface classifying current to take care of different lump sizes, or ranges of lump sizes. The rate of ow of the subsurface current, also, should be properly proportioned with respect to' the volume or capacity of the separating vessel.

It has been pointed out above that the shapel and size, or'capacity, of the separating vessel is such that the ratio of the volume of the vessel to the volume of the subsurface current, per minute of time, is either equal to or less than 5 to 1. 'Ihis range of ratios is more fully explained as follows.

The volumetric capacity of the separating ves-v sel now believed to be most suitable is approxi- If the material that is to be classified by the subsurface current contains no lumps in excess of 3: of an inch, the volume of the subsurface current, per minute of time,

should be from 600 gallons to 800 gallons. If the solids of the material to be classified are from of an in'ch to 1 inch in size, the volume of` the subsurface current should be approximately 1200 gallons per4 minute. If the solids of the material to be classified range up to five inches in size, 2500 gallons of parting liquid should be delivered to the separating vessel as a subsurface current perv minute of operating time. If the solids range as high as eight inches in size, from 3200 to 3500 gallons per minute should be delivered as a subsurface current. The vilow controlling and regulating valve ||6 is manipu- 10 lated to provide the desired volume for the subsurface current. i

The rate of ow of the parting liquid to the starting material feed trough 34 is not very critical. 'I'his liquid is merely employed to wet down the starting material and flume it through l the trough 34.

It will be appreciated, by persons skilled in 4this art, that parting, or heavy density, liquid can only be maintained stabilized at a particular specific gravity throughout its entire mass by preventing the comminuted particles of the dens ity producing medium from settling in the liquid mass. It is apparent, therefore, that if no means are provided for maintaining the heavy density medium stirred up or agitated in the separating vessel of this apparatus, the comminuted particles will settle toward the bottom of the separating vessel and the specific gravity of the liquid in the vessel will increase from the top to the bottom.

The recirculating of the parting, or heavy density, liquid in the separating vessel through the medium of the liquid delivery lines to the subsurface current inlet 36k and the starting material feed trough 34 will function to maintain the comminuted particles properly suspended in the major portion of the separating vessel so that the specic gravity of the surface portion of the body of liquid may be continuously maintained. This 'same specic gravity will be maintained throughout the area that is influenced or affected by the subsurface current. The rotation of the conveyor wheel, also, will function to stabilize the density of the liquid.

It will be appreciated, however, that the bottom portion of the separating vessel which is located below the path of the subsurface current has a tendency to function as a trap for th'e comminuted heavy density particles. If the conveying wheel does not keep this bottom portion ofthe body of heavy density liquid stirred up or agitated sulciently to keep the comminuted particles in proper suspension, the specific gravity of this bottom portion of the body of liquid will be greater than the desired value. This zone or area of questionable stability, or specific gravity, is controlled in a novel way to provide different desired specic gravities, or what might be better termed different artificial specific gravities, in the feeding zones for the two annular series of conveying pockets provided by the conveyor wheel. This control of the specic gravities in these two feeding zones is obtained by the two ducts 26 and 21 and the connections between their bottom vopenings and the liquid circulating pipe lines nected to the discharge side of the pump |04.

while the pipe line is connected to the inlet side of the pump ||2. Consequently, the two branch lines |24 and |25 for the pipe line |06 will be under pressure while the branch lines |30|32|34 and |3||33|35 will be subjected to the suction of the pump ||2 through their connection with the pipe line Consequently, by opening the valves |26 and V|21 and closing the valves |36 and |31, the separating vessel ducts 21 and 26 respectively will be subjected to an updraft 'of liquid. Conversely, if valves |26 and |21 are closed and valves |36 and |31 are opened, the separating vessel ducts 21 and 26 respectively will be subjected to downdrafts of liquid. It will be apparent, also, that these four valves can be manipulated so that an updraft of liquid can be provided in one of the aman? 11 ducts 26 and 21 while a downdraft of liquid can be provided in the other duct.

When a downdraft of liquid is provided in one of the ducts 26 or 21, the liquid in the separating vessel in the zone associated with the circular series of conveyor wheel pockets aligned with this duct will be influenced in a way to create a lower, artificial specific gravity in this zone. That is to say, the comminuted particles suspended in the liquid in this zone will be prevented from accumulating in such a manner as to increase the specific gravity of the liquid in the zone above the normal value. Additionally, the liquid in the zone associated with the circular series of conveyor wheel pockets aligned with the duct through which a, downdraft of liquid is taking place will flow downwardly toward the duct and this downward flow or current will tend to draw solids into the series of conveyor wheel pockets.

When an updraft of liquid is provided through one of the ducts 26 or 21, this upward flow of liquid through the zone associated with the circular series of conveyor wheel pockets aligned with the duct will have a tendency to back up the comminuted particles in the zone and `will have a tendency to create an artificial specific gravity that is greater than the 1.40 value prevailing above this zone. Also, the upward draft or current of liquid through this conveyor wheel feeding zone will have a tendency to exclude the lumps of solids of lower specific gravity from the conveyor wheel pockets that pass through this feeding zone.

It, further, will be appreciated that proper liquid drafts, either up or down, can be produced through the ducts 26 and 21 to assure the maintenance of a suitable specific gravity in either or both of the feeding zones for the two circular series of conveying pockets provided by the conveyor wheel.

The disclosure provided by Fig. 7 has not bee referred to above in connection with the description of the apparatus although many of the structural elements are disclosed in this figure. This figure has been especially prepared for use in describing the hydraulic separating or classifying method, or methods, which can be performed by the apparatus. For that reason, some structural elements have been omitted and lines have been added to indicate in a general way the paths of movement of the sinking solids as a result of the classifying influence produced by the diagonal subsurface current.

Let us first consider that the apparatus. disclosed in Fig. 'I is being employed for carrying out a method of providing a three product separation of' such starting material as run-of-the-mine coal. This starting or raw coal will include purer coal. free valueless slate. and coal laminated or physically combined with impurities, such as slate.

The purer coal will float when immersed in a liquid body or bath having a specific gravity of, for example, 1.40. All of the remaining starting material will sink when immersed in this body of liquid. Consequently. the purer coal will be separated from the pure refuse, or free slate, and from the coal that is physically combined in some way with impurities. This impure coal should be classified as middlings and should be separated from the refuse. or free slate.

The path-of-movement lines presented within the separating vessel in Fig. 7 have indicia applied thereto which cover lump sizes ranging from 1 12 inch to 5 inches. The indicia, also, indicates speciflc gravities for the different sized lumps.

Let us now assume that the raw or starting coal is delivered to the feed trough '34 and is iiumed, down this trough by the parting, or heavy density, liquid that is delivered to the trough through the manifold branches |23.

This raw or starting coal will be plunged into the zone A of the parting liquid bath in the separating vessel. The liquid in this zone A is relatively quiet and is consistently maintained at a specific gravity of 1.40. Therefore, all of the purer coal will float on the surface of the bath of liquid while the solids having specific gravities in excess of 1.40 will start to sink. The float coal will be carried across the separating vessel by the transverse flow or current that is produced by the feeding of the parting liquid through the inlet opening 33 and the discharge of the parting liquid over the weir 31 into the discharge trough 39. This cross current will carry the float coal to the discharge opening 38 where it will be flushed over the Weir 31 into the trough 39.

The material that has been separated from the float coal will sink through the zone A until it passes into the diagonally upwardly directed subsurface current of liquid that is produced by the flow of liquid through the inlet opening 36. Because solids from 1 inch to 5 inches in size make up the sink material, the parting liquid should be fed through the inlet opening 36 at approximately 2500 gallons per minute.

This subsurface current will effect separation, or classification, of the sink material into refuse and middlings products in accordance with the size, shape and specific gravity of the sinking solids. This classification, in other words, is determined by the sinking velocities of the different pieces and the relative transverse or horizontal displacement thereof by the diagonal subsurface current. The reference character B is employed in Fig. 'I to generally indicate or designate the classifying zone of the subsurface current. After the sinking solids have passed through the zone B, they will continue to sink through the two zones which are designated by the reference characters C and D.

The path-of-movement lines, with their lump size and specific gravity indicating indicia disclose the fact that the refuse, or heavier lumps of slate, will sink into the zone D while the middlings, or contaminated coal, will sink into the zone C. The adjustable divider 11, which has been omitted from Fig. 7 for the sake of clarity, may be adjusted to effect a further classification of the refuse and middlings that sink into the zones D and C respectively.

The subsurface current, flowing through the zone B, effects no direct control or influence over the refuse and middlings solids that are settling or sinking through the zones D and C. However, the zone D is indirectly affected by the entraining or aspirating action of the subsurface current while zone C is indirectly affected or influenced by the downward deflection of some of the liquid of the subsurface current that impinges against the end wall l5 ofthe separating vessel. The indirect entraining or aspirating action produced in the zone D has a tendency'to retard the sinking of solids in this zone and, for that reason, helps to separate out some of the smaller sized lighter lumps for delivery to the zone C through which the middlings are intended to pass. The downward deflection of liquid from the subsurface current through the zone C has a tendency to 13 deiiect the lighter lumps downwardly through thlszone. The indirect effect of the subsurface current on the zones C and D, therefore, furthers the desired classification of the sinking solids into the desired refuse and middlings products.

It has been explained above that artificial' specific gravity conditions can be created in the zone C and D by establishing updrafts or downdrafts through the ducts-26 and 21. Consequently, the desired artificial specific gravity conditions will be set up in the zones C and D to assure proper accomplishment of the desired classification of the solids into refuse and middlings products. Of course, the refuse will settle through the zone D into the circular series of conveyor wheel pockets that are fed from this zone while the middlings will be delivered to the circular series of conveyor wheel pockets that are associated with the zone C.

The apparatus embodying this invention may be operated, without structural modification, to carry out two different methods of effecting two product separation of solids. These two methods now will be described.

If the starting material is to be separated into two products of differentl specific gravities, the parting liquid used in the separating vessel should have a specific gravity that falls between the speciiic` gravities of the two desired products. By completely closing the valve H6, so as to stop the subsurface current, the starting material can be separated into sinks and floats merely by the action of the parting, or heavy density, liquid. The float material will pass over the weir 31 into the discharge trough 39 while the sink material will settle through the liquid body or bath into the pockets of the conveyor wheel. The divider plate 1l, not shown in Fig. 7, may be moved into the position illustrated in Fig. 1. or even further to the right, to assist in deecting some of the sink product into the lefthand circular series of conveyor wheel pockets to accomplish a more uniform loading of both series of pockets.

The method just described, therefore, will effect a two product separation of solids purely by the sink and float action of the parting, or heavy density, liquid.

'I'he starting material can be separated, or classified, into two products by merely employing the action of the subsurface current and without relying on the specic gravity of the liquid to eilect any separation of the product. That is to say, the liquid employed in the separating vessel may be plain water, or any other liquid having a specific gravity lower than the specific gravity of any of the solids to be classified. The operation of the apparatus to carry out this type of tuvo product separationwill be the same as that described above for the classification of the sink solids into refuse and middlings if the liquid used in the separating vessel has a specific gravity that is higher than plain water. If plain water is used in the separating vessel, the ducts 26 and 21 cannot be employed for creating updrafts c-r downdrafts in the zones D and C to provide arti*- cial specific gravity conditions in these zones.

It is to be understood that we do not desire to be limited to the exact order of method steps as they have been disclosed, for variations and modifications of the same, which fall within the scope of the accompanying claims, are contemplated.

It, further, is to be understood that the particularY type of apparatus herein shown and described is to be taken as a preferred example of the invention, and that various changes in the shape, size,

without departing from the spirit of the invention or the scope of the subjoined claims.

Having thus described the invention,- we claim:

1. A method of hydraulically classifying solids into separated products of different specific gravities, comprising introducing the starting mixture of solids into a body of parting liquid of a speciiic gravity which will float one of the desired products while permitting the remaining solids to sink, withdrawing the float product from the body of liquid, creating a subsurface current through the body of liquid in a direction crossing the path of the sinking solids to relatively laterally displace the slower sinking solids from the more rapidly sinking solids to produce two additional products, creating an updraft in the parting liquid in the path of the more rapidly sinking solids to assist :in separating therefrom the slower sinking solids, .creating a downdraft in the parting liquid in the path of the slower sinking solids to accelerate the rate of sinking of such solids, and separately withdrawing these additional products from the body of liquid.

2. A method of hydraulically classifying solids into separated products of different specific gravities, comprising introducing the starting mixture of solids into a body of parting liquid of a speciiic gravity which will oat one of the desired products while permitting the remaining solids to sinkl withdrawing the float product and some of the liquid from the body of liquid, introducing into the body of liquid a stream of the same speciic gravity liquid to create a subsurface current crossing the path of the sinking solids to relatively laterally displace the slower sinking solids from the more rapidly sinking solids to produce -two additional products, creating an updraft in the parting liquid in the path ofthe more rapidly sinking solids to assist in separating therefrom the slower sinking solids, creating a downdraft in the parting liquid in the path of the slower sinking solids to accelerate the rate of sinking of such'solids, andA separately withdrawing these additional products from the body'of liquid. y

3. A method of hydraulically classifying solids into separated products of diierentspecic gravities, comprising producing a body of parting liquid of a specific gravity `which will float vonly one of the desired products, introducing the starting mixture of solids and some of the same parting liquid into the body of liquid at a relatively quiescent zone located at one top marginal portion of said body so that the float product will remain at the surface of the liquid body while the balance of the solids, will sink, ywithdrawing the float product and some of the parting liquid from the opposite top marginal portion of said body,

separating the withdrawn parting liquid from the oat product and re-introducing said liquid into the body of liquid to create a subsurface current crossing the path 0f the sinking solids to relatively laterally displace the slower sinking solids from the more rapidly sinking solids to produce two additional products, creating an updraft in the parting liquid in the path of the more rapidly sinking solids to assistin separating therefrom the slower sinking solids, creatinga downdraft in the parting liquid in the path of the slower sinking solids to accelerate the rate of sinking of such solids,v and separately withdrawing these additional products from the body of liquid.

4. A method of hydraulically classifying solids into separated products of different specific gravf ities, comprising producing a body of parting liquid of a specific gravity which will iioat only one of the desired products, introducing the starting mixture of solids and some of the same parting liquid into the body of liquid at a relatively quiescent zone located at one top marginal portion of said body so that the float product will remain at the surface of the liquid body while the balance of the solids will sink, withdrawing the float product and some of the parting liquid from the opposite top marginal portion of said body, separating the withdrawn parting liquid from the float product and re-introducing said liquid into the body of liquid to create a subsurface current crossing the path of the sinking solids to relatively laterally displace the slower sinking solids from the more rapidly sinking solids to produce two additional products, creating an updraft in the parting liquid in the path of the more rapidly sinking solids to assist in separating therefrom the slower sinking solids, creating a downdraft in the parting liquid in the path of the slower sinking solids to accelerate the rate of sinking of such solids, and separately withdrawing these additional products from the body of liquid while permitting parting liquid to drain from these additional products directly into the body of liquid.

5. A method of hydraulically classifying solids into separated products of different specic gravities, comprising providing a body of parting liquid consisting of water mixed with a density increasing medium, controlling the specific gravity of the body of liquid so that it will float only one of the desired products, introducing the starting solids into the body at one top margin thereof so that the float product will remain at the surface while the balance of the solids will sink, withdrawing the float productl from the opposite top margin of the body of liquid, introducing parting liquid into the bottom of the body of liquid to create an updraft in a zone of the body of parting liquid on the side or margin thereof at which the starting solids are introduced to separate slower sinking solids from more rapid sinking solids in said zone, withdrawing parting liquid from the bottom of the body of liquid to create a downdraft in a zone of the body of parting liquid on the side or margin thereof at which the float product is withdrawn to accelerate the rate of sinking of solids in said zone, and separately withdrawing the settled solids from said different zones.

6. A method of hydraulically classifying solids into separated products of diierent specific gravities, comprising producing a body of parting liquid consisting of water mixed with a density increasing medium, controlling the speciiic gravity of the body of liquids so that it will float only one of the desired products, introducing the starting solids into the body at one top margin thereof so that the iloat product will remain at the surface while the balance of the solids will sink, withdrawing the float product from'the opposite top margin of the body of liquid, dividing the body of parting liquid below its top surface into two settling zones for the sinking solids, introducing parting liquid into the bottom oi the body of liquid to create an updraft in the parting liquid ln one oi' said zones to exclude from said 'zone the slower sinking solids, withdrawing part- 'ing liquid from the bottom of the body of liquid to create a downdraft in the parting liquid in the other of said zones to accelerate the rate of settling of the slower sinking solids in said zone, and separately withdrawing the settled solids from said diilerent zones by moving them upwardly 16 through the body of liquid to a location above said body so that the parting liquid will drain from these withdrawn solids directly into the body of liquid.

7. A method of hydraulically classifying solids into separated products of diilerent specitlc gravities, comprising producing a body of parting liquid consisting of water mixed with a density increasing medium, controlling the specific gravity of the body of liquid so that it will iloat only one of the desired products, introducing the starting solids and some of the parting liquid into the body at one top margin thereof so that the float product will remain at the surface while the balance of the solids will sink, withdrawing the iloat product and some of the parting liquid from the opposite top margin of the body of liquid, separating the withdrawn parting liquid from the float product and re-introducing said liquid in to the body of liquid, dividing the body of parting liquid below its top surface into two settling zones for the sinking solids, introducing a parting liquid into the bottom of the body of liquid to create an updraft in the parting liquid in one of said zones to exclude from said zone the slower sinking solids, withdrawing parting liquid from the bottom of the body of liquid to create a downdraft in the parting liquid in the other of said zones to accelerate the rate of settling of the slower sinking solids in said zone, and separately withdrawing the settled solids from said different zones.

8. A method of hydraulically classifying solids into separated products of different speciiic gravities, comprising introducing the starting mixture f of solids into a body of liquid through which the solids will sink at different velocities, creating a subsurface current through the body of liquid in a direction crossing the path of the sinking solids to separate by relative lateral displacement the slower sinking solids from the more rapidly sinking solids so that the separated solids, after passing through the subsurface current, will settle into different zones in the bottom of the body of liquid, creating an updraft in the parting liquid in the path of the more rapidly sinking solids to assist in separating therefrom the slower sinking solids, creating a downdraft in the parting liquid in the path of the slower sinking solids to accelerate the rate of sinking of such solids, and separately withdrawing the solids from said different zones.

9. Apparatus for hydraulically classifying solids into separated products of different specific gravities, comprising a separating vessel in which is placed a parting liquid of a specific gravity which will float only one of the desired products while permitting the remaining solids to sink, means for feeding the starting mixture of solids into the vessel, a weir over which the oat product and some of the parting liquid will pass in leaving the vessel, means for separating' the parting liquid from the float product, means i'or recirculating the separated parting liquid to create a subsurface current through the liquid .in the vessel in a direction crossing the path of the sinking solids to eiect relative lateral displacement of the slower sinking solids from the more rapidly sinking solids to provide two additional products, means fox creating an' updraft in the parting liquid in one portion .of the separating vessel, means for creat- 1 ing a downdraft in the parting liquid in a different solids into separated products of different specic gravities, comprising a separating vessel in which is placed a parting liquid of a specific 'gravity which will oat only one of the desired products while permitting the remaining solids to sink, means for feeding the starting mixture of solids into the vessel, a weir over which the oat product and some of the parting liquid will pass in leaving the vessel, means for separating the parting liquid from the oat product, means for recirculating the separated parting liquid to create a subsurface current through the liquid in the vessel in a direction which will cause the current to terminate at the weir, whereby the current will relatively laterally displace the slower sinking solids from the more rapidly sinking solids to provide two additional products and Lwill assist in the discharge of the float product over the weir, means for creating an updraft in the parting liquid in one portion of the separating vessel, means for creating a downdraft in the parting liquid in a different portion of the separating vessel, and means for removing these additional products from the vessel.

11. Apparatus for hydraulically classifying solids into separated products of different specific gravities, comprising a separating vessel in which is placed a parting liquid of a specific gravity which will float only one of the desired products while permitting the remaining solids to sink, a trough for feeding the starting mixture of solids into the vessel, a trough for discharging the oat product and some of the parting liquid from the vessel, means for separating the parting liquid from the float product, means for returning the separated parting liquid to the vessel by delivering it to the said feed trough to fiume the starting solids and by delivering it directly to the vessel in a manner to create a subsurface current through the liquid in the vessel in a direction crossing the path of the sinking solids to effect relative lateral displacement of the slower sinking solids from the more rapidly sinking solids to provide two additional products, means for creating an updraft in the parting liquid in one portion'o'f the separating vessel, means for creating a downdraft in the parting liquid in a different portion of the separating vessel, and means for removing these additional products from the vessel.

12. Apparatus for hydraulically classifying solids into separated products of different specific gravities, comprising a separating vessel in which is placed a parting liquid of a specific gravity which will float only one of the desired products while permitting the remaining solids to sink, means for feeding the starting mixture of solids into the vessel, a weir over which the oat product and some of the parting liquid will pass in leaving the vessel, means for separating the parting liquid from the oat product, means for recirculating the separated parting liquid to create a subsurface current through the liquid in the vessel in a direction crossing the path of the sinking solids to effect relative lateral displacement of the slower sinking solids from the more rapidly sinking solids to provide two additional products, a conveyor wheelv for removing these additional products from the vessel comprising WO parallel endless series of conveying pockets having perforated peripheral walls arranged to travel paths which will intersect the paths of the two relatively displaced sinking products so'that these products will feed into the pockets, means for producing an updraft of parting liquid through the perforated peripheral wall of one of said endless receive their sink product, and means for producing a downdraft of parting liquid through the perforated peripheral wall of the other series of pockets as they are positioned to receive their sink product.

13. Apparatus for hydraulically classifying solids into separated products of different specic gravities, comprising a separating vessel in which is placed a parting liquid of a specific gravity which will float only one of the desired products while permitting the remaining solids to sink, a trough for feeding the starting mixture of solids into the vessel, a trough for discharging the float -product and some of the parting liquid from the vessel, means for separating the parting liquid from the float product, means for returning the separated parting liquid to the vessel by delivering it into the said feed trough to fiume the starting solids and by delivering it directly to the vessel in a manner to effect relative displacement of the slower sinking solids from the more rapidly sinking solids to provide two additional products, a conveyor wheel for removing these additional products from the vessel comprising two parallel endless series of conveying pockets having perforated peripheral walls arranged to travel paths which will intersect the paths of the two relatively displaced sinking products so that these products will feed into the pockets, means for producing an updraft of parting liquid through the perforated peripheral wall of one of said endless series of pockets as said pockets are positioned to receive their sink product, and means for producing a downdraft of parting liquid through the perforated peripheral wall of the otherv series of pockets as they are positioned to receive their sink product.

14. Apparatus for hydraulically classifying solids into separated products of different specific gravities, comprising a separating vessel to receive a body of parting liquid; a feed trough for the starting mixture of solids connected to the vessel; a trough connected to the vessel through which a float product is discharged with a relatively constant volume of the parting liquid; a sump for receiving the withdrawn parting liquid; two draft ducts communicating with the bottom of the vessel, a recirculating piping system for returning the parting liquid to the vessel from the sump, said piping system comprising two main return lines, a pump in each of said lines, one of said pumps having its inlet connected to its return line while the other pump has its outlet connected to its return line, a common connecting line between both of said main return lines, downstream of both pumps, and a side of the vessel to produce asubsurface classifying current through the body of parting liquid in the vessel, and a flow regulating valve in said common connecting line; a pair of branch lines each connected at its opposite ends to the two main return lines and intermediate its ends to different ones of the draft ducts communicating with the bottom of the vessel, valve means in each of said branch lines for selectively connecting its draft duct to either of the main return lines, and means for removing settled solids from the bottom portion of the vessel.

15. Apparatus for hydraulically classifying solids into separated products of different specific gravities, comprising a separating vessel to receive a body of parting liquid; a feed trough for the starting mixture of solids connected to the vessel; a trough connected to the vessel through which a oat product is discharged with a rela.- tively constant volume of the parting liquid; a sump for receiving the withdrawn parting liquid; two draft ducts communicating with the bottom of the vessel, a recirculating piping System for returning the parting liquid to the vessel from the sump, said piping system comprising two main return lines, a pump in each of said lines, one of said pumps having its inlet connected to its return line while the other pump has its outlet connected to its return line, a common connecting line between both of said main return lines, downstream of both pumps, and a side of the vessel to produce a subsurface classifying current through the body of parting liquid in the vessel, and a flow regulating valve in said common connecting lines; a pair of branch lines each connected at its opposite ends to the two main return lines and intermediate its ends to different ones of the draft ducts communicating with the bottom of the vessel, valve means in each of said branch lines for selectively connecting its draft duct to either of the main return lines, and a conveyor wheel partially submerged in the -body ofliquid in the vessel for removing settled solids from the bottom portion of the vessel.

16. Apparatus for hydraulically classifying solids into separated products of different specic gravities, comprising a separating vessel to receive a body of parting liquid; a feed trough for the starting mixture of solids connected to the vessel; a trough connected to the vessel through which a float product is discharged with a relatively constant volume of the parting liquid; a sump for receiving the withdrawn parting liquid; two draft ducts communicating with the bottom of the vessel, a recirculating piping system for returning the parting liquid to the vessel from the sump, said piping `system comprising two main return lines, a pump in each of said lines, one of said pumps having its inlet connected to its return line while the other pump has its outlet connected to its return line, a common connecting line between both of said main return lines, downstream of both pumps, and a side of the vessel to produce a subsurface classifying current through the body of parting liquid in the vessel, a branch line between said common connecting line and the feed trough to deliver fluming liquid to said trough, and separate valves for regulating the flow of liquid to the vessel and to the feed trough; a pair of branch lines each connected at its opposite ends to the two main return lines and intermediate its ends to different ones of the draft ducts communicating with the bottom of the vessel, valve means in each of said branch lines for selectively connecting its draft duct to either of the main return lines, and means for removing settled solids from the bottom portion of the vessel.

17. Apparatus for hydraulically classifying solids into separated products of different specific gravities, comprising a separating vessel to receive a body of parting liquid; a feed trough for the starting mixture of solids connected to the vessel; a trough connected to the vessel through which a iioat product is discharged with a relatively constant volume of the parting liquid; a sump for receiving the withdrawn parting liquid; two draft ducts communicating with the bottom of the vessel, a recirculating piping system for returning the parting liquid to the vessel from the sump, said piping system comprising two main return lines, a pump in each of said lines, one of said pumps having its inlet connected to its re- 20 turn line while the other pump has its outlet connected to its return line, a common connecting line between both of said main return lines, downstream of both pumps, and a side of the vessel to produce a subsurface classifying current through the body of parting liquid in the vessel. a branch line between said common connecting line and the feed trough to deliver fiuming liquid to said trough, and separate valves for regulating the flow of liquid to the vessel and the feed trough; a pair of branch lines each connected at its opposite ends to the two main return lines and intermediate its ends to different ones of the draft ducts communicating with the bottom of the vessel, valve means in each of said branch lines for selectively connecting its draft duct to either of the main return lines, and a conveyor wheel partially submerged in the body of liquid in the vessel for removing settled solids from the l bottom portion of the vessel.

18. Apparatus for hydraulically classifying solids into separated products of different specific gravities, comprising a separating vessel to receive a body of parting liquid; a feed trough for the starting mixture of solids connected to the vessel; a trough connected to the vessel through which a oat product is discharged with a relatively constant volume of the parting liquid; a. sump for receiving the withdrawn parting liquid; two upwardly opening liquid draft ducts formed in the bottom of the vessel; a recirculating piping system for returning the parting liquid to the vessel from the sump, said piping system comprising two main return lines, a pump in each of said lines, a common connecting line between both of said main return lines, downstream of both pumps, and a side of the vessel to produce a subsurface classifying current through the body of parting liquid in the vessel, a flow regulating valve in said common connecting line, a pair of branch lines each of which is connected with a draft duct of the vessel intermediate its ends, said branch lines each being connected at one end with one of the main return lines upstream of its pump and at its other end with the other main return line downstream of its pump, and two flow regulating valves in each branch line located at opposite sides of the connection with the draftduct; and means for removing from the bottom portion of the vessel solids which are classified by said subsurface current.

19. Apparatus for hydraulically classifying solids into separated products of diierent specific gravities, comprising a. separating vessel in which is placed a parting liquid of a specific gravity which will oat one of the desired products while permitting the remaining solids to sink, means for feeding the starting mixture of solids into the vessel, a weir over which the float product will pass in leaving the vessel, a conveyor wheel for removing the settled solids from the bottom of the vessel comprising an endless series of conveying pockets, having perforated peripheral walls, arranged to travel a path which will intersect the path of the sinking solids so that such solids will be fed into the pockets. means for introducing parting liquid into the body of liquid at a location above the path of intersection of the conveying pockets with the sinking solids, means for producing an updraft of parting liquid through the perforated peripheral walls of said series of pockets as said pockets are positioned to receive the sinking solids, and means for continuously withdrawing parting liquid from the bottom portion o1' the vessel at a desired constant ids into separated products of diierent specific l gravities, comprising an open topped separating vessel in which is maintained, at a predetermined level, a single body of parting liquid having a specic gravity which will float only one of the desired products while permitting all the remaining solids to sink, means for delivering the starting mixture of solids and some parting liquid into the body of liquid at one` end of the vessel to bring about a separation of floatable solids from sinkable solids, means for withdrawing the oatable solids and some of -the parting liquid from the body of liquid at the opposite end of the vessel, a centrally open wheel having a perforated peripheral wall and flights cooperating with said wall to form a circular series of inwardly opening conveyor pockets, means for rotatably supporting said wheel partially submerged in the body of parting liquid with its axis of rotation paralleling the direction of movement of the floatable solids from the delivering means to the withdrawing means so that the sinking solids will be stopped in the conveyor pockets by said perforated wall and will be elevated therein to the top of the wheel, means for introducing additional parting liquid into the bottom of the vessel below the periphery of the wheel so that said liquid will pass upwardly through the submerged conveyor pockets of said wheel in flowing toward the withdrawing means, means for rotating-jsaid wheel, and conveyor means passing in an'faxially direction beneath the top of the wheel to receive and carry olf the solids discharged from the inwardly opening pockets.

21. Apparatus for hydraulically classifying solids into products of different specific gravities, comprising a vessel in whichis placed a parting liquid of a specific gravity which will float one product to effect its separation from the remaining solids, means for feeding the starting mixture of solids and somevparting liquid into the vessel, a discharge weir over which the float product is flushed by parting liquid flowing from the vessel, an annular conveyor wheel, comprising a circular series of flights forming radially inwardly opening conveying spaces therebetween, positioned partly within and partly above the parting liquid in the vessel for lifting only the said remaining solids from the parting liquid, means for removing only said lifted solids from the vessel extending into the open central portion of the annular conveyor wheel for receiving from its conveying spaces the solids that are lifted therein out of the parting liquid and are spilled radially inwardly, and means for introducing additional parting liquid into the bottom of the vessel below the periphery of the conveyor wheel so that said liquid will pass upwardly through the submerged conveying spaces of the wheel in owing toward said discharge weir.

22. Apparatus for hydraulically classifying solids into products of different specic gravities, comprising an open topped vessel in which is placed a parting liquid of a specific gravity which will float one product to eiect its separation from the remaining solids, said vessel being of rectangular shape in plan formed of parallel end Walls and combined side and bottom walls which include curved intermediate portions and bottom portions that converge downwardly to form a fluid duct, an annular conveyor wheel, comprising a circular series of flights forming radially inwardly opening conveying spaces therebetween, for lifting only the remaining solids from the parting liquid, means for rotatably supporting the conveyor wheel positioned partly within and partly above the parting liquid in the vessel with its periphery relatively closely approaching the curved intermediate portions of said combined side and bottom walls. perforate wall means cooperating with the periphery of the conveyor Wheel for preventing solids positioned in the submerged conveying spaces of the wheel from sinking into the aforesaid fluid duct of the vessel, means for feeding a starting mixture of solids and some parting liquid into the vessel, a discharge weir over which the float product is flushed by the parting liquid flowing from the vessel, means extending into the open central portion of the annular conveyor wheel for removing from its conveying spaces the solids that are lifted therein out of the parting liquid and are spilled radially inwardly, and means for introducing additional parting liquid into the vessel through said iluid duct so that said liquid will pass upwardly through the perforate wall means and the submerged conveying spaces of said wheel in flowing toward said discharge Weir.

23. Apparatus for hydraulically classifying solids into products of different specic gravities, comprising a vessel in which is placed a parting liquid of a specific gravity which will float one product to effect its separation from the remaining solids, means for feeding the starting mixture of solids and some parting liquid into the vessel, a discharge weir over which the float product is ushed by parting liquid flowing from the vessel, an annular conveyor wheel, comprising a circular series of flights forming radially inwardly opening conveying spaces therebetween, positioned partly within and partly above the parting liquid in the vessel for lifting only said remaining solids from the parting liquid, perforate Wall means cooperating with the periphery of the conveyor wheel for preventing solids positioned in the submerged conveying spaces of the wheel from sinking into the bottom portion of the vessel, means for removing from the vessel only the solids that are lifted by said wheel, and means for introducing additional parting liquid into the bottom of the vessel below the periphery of the conveyor wheel for producing an updraft of liquid through the submerged conveying spaces of the wheel for excluding from said spaces solids of too low specific gravity.

24. Apparatus for hydraulically classifying solids into products of different specific gravities comprising an open topped vessel in which is placed a parting liquid of a specific gravity which will iloatv one product to eiect its sparation from the remaining solids, said vessel being of rectangular shape in plan formed of parallel end walls and combined side and bottom walls which merged conveying spaces of the wheel from sinking into the aforesaid fluid duct of the vessel, means for feeding the starting mixture of solids and some parting liquid into the vessel, a discharge Weir over which the float product is ushed by parting liquid flowing from the vessel, means for removing from the vessel only the solids that are lifted by said wheel, and means for introducing additional parting liquid into the vessel through said fluid duct for producing an updraft of liquid through the submerged conveying spaces of the wheel for excluding from said spaces solids of too low specific gravity.

25. Apparatus for hydraulically classifying solids into products of different specific gravities,.

comprising an open topped vessel in which is placed a parting liquid of a specific gravity which .will float one product to effect its separation from the remaining solids, said vessel being of rectangular shape in plan formed of parallel end walls and combined side and bottom walls which include curved intermediate portions and bottom portions that converge downwardly to form a fluid duct, an annular conveyor wheel comprising a circular series of flights forming radially inwardly opening conveying spaces therebetween for lifting only the remaining Solids from the parting liquid, means for rotatably supporting the conveyor wheel positioned partly within and partly above the parting liquid in the vessel with its periphery relatively closely approaching the curved intermediate portions of the combined side and bottom walls, curved imperforate plates mounted in the vessel in spaced concentric relation to the curved intermediate portions of said combined side and bottom walls for cooperating therewith to form encased paths for the ascending and descending flights of the conveyor wheel, perforate wall means cooperating with the periphery of the conveyor wheel for preventing solids positioned in the submerged conveying spaces of the wheel from sinking into the aforesaid fluid duct of the vessel, means for feeding the starting mixture of solids and some parting -liquid into the vessel, a discharge weir over which the float product is flushed by parting liquid flowing from the vessel, means for removing from the vessel only the solids that are lifted by said wheel, and means for introducing additional parting liquid into the bottom of the vessel below the periphery of the conveyor wheel for producing an updraft of liquid through the submerged conveying spaces of the wheel for excluding from said spaces solids of too low specific gravity.

26. Apparatus for hydraulically classifying solids into products of different specific gravities, comprising a vessel in which is placed a parting liquid of a specific gravity which will float one product to effect its separation from the remaining solids, means for feeding the starting mixture of solids and some parting liquid into one end of the vessel to bring about a separation of oatable solids from sinkable solids, a Weir over which the floatable solids are flushed by the parting liquid flowing from the opposite end of the vessel, a centrally open conveyor wheel having a perforate peripheral wall and flights cooperating with said wall to form a circular series of inwardly opening conveyor pockets, means for rotatably supporting said wheel positioned partly within and partly above the parting liquid with its axis of rotation paralleling the direction of movement of floatable solids from the delivering means to the said Weir so that the sinking solids will be stopped in the conveyor pockets by said perforate wall and will be elevated therein to the top of the wheel, means for introducing additional parting liquid into the bottom of the vessel below the periphery of the conveyor wheel to create an updraft through the perforated peripheral wall and the conveyor pockets of the wheel in flowing toward said discharge weir, means for rotating said conveyor wheel, and conveyor means extending in an axial direction into tlie open central portion of the wheel to receive and carry oil the solids that are lifted therein from the parting liquid and are spilled radially lnwardly from the inwardly opening conveyor pockets.

27. Apparatus for hydraulically classifying solids into products of different specific gravities, comprising a vessel in which is placed a single body of parting liquid of a specific gravity which will float only one product to eiect its separation from all the remaining solids, means for feeding the starting mixture of solids and some parting liquid into one end of the vessel to bring about a separation of floatable solids from sinkable solids, a Weir over which the floatable solids are flushed by the parting liquid flowing from the opposite end of the vessel, a centrally open conveyor wheel having a perforate peripheral wall and flights cooperating with said wall to form a circular series of inwardly opening conveyor pockets, means for rotatably supporting said wheel positioned partly within and partly above the parting liquid with its axis of rotation paralleling the direction of movement of the floatable solids from the delivering means to the said Weir so that the sinking solids will be stopped in the conveyor pockets by said perforate wall and will be elevated therein to the top of the wheel, means for introducing parting liquid into the bottom of the vessel below the periphery of the conveyor wheel to create an updraft through the perforate peripheral wall and the conveyor pockets of the wheel in flowing toward said discharge Weir, means for introducing additional parting liquid into the portion of the body of liquid located within the submerged portion of the wheel, means for rotating said wheel, and conveyor means extending in an axial direction into the open central portion of the wheel to receive and carry oft the solids that are lifted from the parting liquid and are spilled radially inwardly from the inwardly opening conveyor pockets.

28. Apparatus for hydraulically classifying sol-I ids into products of different specific gravities, comprising an open topped separating vessel in which is placed a parting liquid of a specific gravity which will float one of the desired prod- -ucts to effect its separation from the remaining solids, said vessel being of rectangular shape in plan formed of parallel end walls and combined side and bottom walls which include curved intermediate portions and bottom portions that converge downwardly to form a fluid duct, means for feeding the starting mixture of solids and some parting liquid into one end of the vessel to bring about a separation of floatable solids from sinkable solids, a Weir over which the oatable solids are flushed by the parting liquid flowing from the opposite end of the vessel, a centrally open conveyor wheel, comprising a circular series of flights forming radially inwardly opening conveying spaces therebetween, for lifting only the remaining solids from the parting liquid,v

means for rotatably supporting said wheel positioned partly within and partly above the parting liquid with its periphery relatively closely approaching the curved intermediate portions of said combined side and bottom walls and with its axis of rotation paralleling the direction of movement of the iloatable solids from the delivering means to the said Weir, perforate Wall means cooperating with the periphery of the conveyor Wheel for preventing solids positioned in the submerged conveying spaces oi the wheel from sinking into the aforesaid duct of the vessel, means for introducing additional parting liquid into the vessel through said duid duct so that said liquid will pass upwardly through the perforated wall means and the submerged conveying spaces of said wheel in iiowing toward said discharge Weir. and an endless conveyor having its active run passing in an axial direction beneath the top pf the wheel to receive and carry oir the solids discharged from the inwardly opening conveying spaces.

- NELSON L. DAVIS.

HILMER N. EKBOM. LAURANCE O MILLARD.

REFERENCES CITED The following references are of record in the ille oi this patent:

UNITED STA'I'ES PATENTS Number Name Date 915,832 Dekker Mar. 23, 1909 1,306,361 Wahl June 10, 1919 10 1,559,938 Chance Nov. 3, 1925 2,150,946 Smith Mar. 21, 1939 2,246,532 Prins June 24, 1941 2,345,513 Trosler Mar. 28, 1944 FOREIGN PATENTS 15 Number Country Date 208,978 Great Britain Jan. 3, 1924 370,564 Great Britain Apr. 14, 1932 451,402 Great Britain Aug. 5, 1935 554,285 Great Britain June 28, 1943 29 680,515 France Jan. 22, 1930 661,897 Germany June 29, 1938 

